Ep# 12 An Interview with Rohit Chakravarty and Pritha Dey.
EP#12 Show notes (Edited).
[Photos courtesy: Rohit Chakravarty. Top-L-R Clockwise: Leisler’s Bat (Nyctalus leisleri), Eastern Barbastelle (Barbastella darjelingensis), .Woolly Horseshoe Bat (Rhinolophus luctus), Kashmir Long-eared Bat (Plecotus wardi), Pearson’s Horseshoe Bat (Rhinolophus pearsonii)]
Lalitha Krishnan: Hi. You’re listening to Episode 12 of the Heart of Conservation Podcast. Your very own podcast from the Himalaya. I’m your host Lalitha Krishnan bringing you stories that keep you connected to our natural world. Today for the first time I am speaking to an interesting young researcher-couple who are both experts in their fields. Pritha Dey and Rohit Chakravarty. Pritha’s doctoral work included the study of insect biodiversity loss due to anthropogenic disturbances. My second guest is Pritha’s husband, Rohit Chakravarty. He is a bat biologist currently pursuing a PhD at the Institute for Zoo and Wildlife Research, in Berlin. I met Pritha during a butterfly workshop in Devalsari, Uttarakhand and her knowledge and presentation on moths just blew me away. And so, I invited them to be guests on my show.
Pritha, Rohit, thank you so much for being on Heart of Conservation Podcast. It’s so fascinating to interview researchers anyway but to interview two who are a couple is a special bonus, I think. It’s intriguing that both of you are researching nocturnal creatures. Both of you have travelled in Uttarakhand in pursuit of your subjects. Let’ start with the basics. So Pritha, why moths?
Pritha Dey: Hi Lalitha, thank you for asking us to talk to you about our research.
Lalitha Krishnan: My pleasure.
Pritha Dey: We are highly interested to talk about our research all the time. It’s new for us that both of us are doing it at the same time. So, I’ll start with my pursuits of moths. I finished my Master and immediately joined Wildlife Institute of India where there was a project to document the diversity of moths in twelve different protected areas. Initially it is was just the excitement to roam about in different places and studying moths but eventually, I started reading about them and learning about moths. What intrigued me most was how diverse they are and at the same time how understudied, they are…being ecologically so important.
Lalitha Krishnan: OK.
Pritha Dey: And the myths that we find in movies, that they are evil creatures are absolutely not true. I wanted to look into that more and yes, that’s why moths.
Lalitha Krishnan: I think you have passed on a little of that love to all of us who heard your presentation at the butterfly workshop. I for one was totally inspired and now want to know more. Rohit how about you?
Rohit Chakravarty: Yes, it’s a privilege to be on HOC. I would simply say I chose bats because more than half of India is busy looking at tigers, leopards, lions, elephants, bears and all other charismatic animals. It started off with me looking for an empty niche for my research but in the end, it just took me beyond that empty niche. As we’re going to talk more about bats, we will hopefully convince the audience that bats are rather extraordinary animals. So more about that as we talk.
Lalitha Krishnan: Definitely. So Pritha, you completed your Ph.D. on the diversity patterns of the Geometridae family of moths along the elevation gradients in the western Himalaya. Could you tell us about this family of moths? And why you studied them in the Himalaya?
Pritha Dey: So, when I started working on the project on moths in the Himalayas, I found this particular family called the Geometridae family or commonly known as the Looper Moths. They are very abundant in mountain habitats. In mountains, you find them in huge numbers and they exhibit amazing variation in wing patterns and are hugely diverse with about 24000 species worldwide. Their taxonomy at the same time is very challenging and interesting. So, my idea was to work in the mountains and merge it with moth-study. So, moths and mountains were the ideal study group for me. I chose the western Himalayas because it’s very interesting biogeographically as the tropical and the temperate elements kind of merge in this part of the country and we find very interesting diversity across all taxa. It is far less diverse than the eastern Himalaya where you find double the number of species of moths or other taxa. Yes, this was very interesting as a study group as well as a study area.
Lalitha Krishnan: Great. And the combination of moths and mountains just works right? And Rohit, correct me if I am wrong, I read that there are a thousand species of bats. Right? How many bat species do we have in India? There are so many myths about bats in general. They are not your everyday mammal either. What is the role of bats in nature?
Rohit Chakravarty: You’re correct about the 1000 species. There are close to 1,300 species of bats in the world. India has about 120 species so we have a really large diversity. And, bats are actually the most diverse group of mammals in India. They even outnumber rodents in India. You’re right. Bats are really not your everyday mammal. They are way more extraordinary than most mammals we come across in our day to day life. They are the only mammals that can fly. They use ultrasound to navigate and they have very long lifespans. From the point, for an animal that is barely the size of a mouse, it actually lives way longer than a tiger would.
Lalitha Krishnan: Wow
Rohit Chakravarty: So, bats are really long-lived and their role in nature… There are two broad categories. There are fruit bats and there are insectivores bats. So, fruit bats pollinate flowers and they disperse seeds of different trees. Some of the flowers that they pollinate include extremely important cash crops like agave and durian. Durian is a very important food plant.
Lalitha Krishnan: Of course.
Rohit Chakravarty: Agave is the plant that is responsible for producing tequila.
Lalitha Krishnan: Yes.
Rohit Chakravarty: So, without bats, there won’t be any tequila. People are also trying to find out more about how bats are important in systems that produce cocoa. There might be many interesting results coming out soon. Insectivores bats eat tons of pest insects, which also include moths, unfortunately.
Lalitha Krishnan: I know, I am going to ask you about that. That’s interesting because considering there are so many bats, we barely see them. And now, you’ve added a twist by saying they pollinate agave. It just made me think, do people actually breed bats by any chance?
Rohit Chakravarty: I’m not sure about it. People don’t breed bats for economic benefits. The only breeding facility that I know of is for research. Not really for economic benefits.
Lalitha Krishnan: OK. Pritha, tell us about the whole moth’s attraction to the flame/the whole moon connection and how many species of moths there are in the world and the Himalayas?
Pritha Dey: We are all very familiar with the phrase,” Like moths to the flame”. Actually, it’s very interesting. It’s very unique to this group of insects that their communication or orientation is towards the light. There’s a theory called the light compass theory which means that they orient their flight towards celestial light. They try to keep the celestial light parallel and orient their flight towards the moon. So if we put any artificial source of light in their pathway, they get confused and try to orient their flight along that pathway along with that artificial light. So you mostly find moths flying in a circular manner around the lights in our houses or street lights if you see them. So that’s the reason. It’s kind of confusing for them so they fly towards the light and we are increasing their confusion by adopting artificial illumination. It’s kind of hampering their ecology.
Lalitha Krishnan: It’s like we know the way home but we use Google maps and end up in some small lane right?
Pritha Dey: Absolutely. Talking about the number of species, India has about 10,000 species of moths. I cannot even imagine how diverse they are. In the Himalayas, the eastern Himalayas have 50-60% of the total diversity, which is 5000-6000 but if you come to the western Himalayas, it’s only 20-30% which is an estimated 2000-3000 species in western Himalaya. You can imagine.
Lalitha Krishnan: Yes, and a major part of it is unexplored right. Both in the west and in the east?
Pritha Dey: Right. When I started out, I was the first person to study moths in Nanda Devi Biosphere Reserve…
Lalitha Krishnan: Oh wow. Nice.
Pritha Dey: …to document them properly. So, such important areas are known for other kinds of wildlife but we don’t know much about moths from such a biodiverse state like Uttarakhand.
Lalitha Krishnan: I’m glad you’re doing that and you can have a lifetime of doing that if you want. There are so many moths. Rohit you did mention that bats are the only mammals that fly. Do they migrate like birds do?
Rohit Chakravarti: They do and we know very little about that in India. Most of the studies on bat migration come from Europe and the US. Because the bat’s flight is not as efficient as that of birds, they cannot fly to the same order as birds do. Some birds can migrate from one pole to the other but bats are not capable of that. The maximum distance that they can cover is about 1000-3000 km.
Lalitha Krishnan: That’s quite a bit.
Rohit Chakravarty: That itself is a lot for an animal of that size. The interesting part though about bat migration is that unlike birds that migrate to remain active in a warmer climate, a lot of bats actually migrate and then they hibernate in much warmer conditions and much cooler conditions. So, bats do all sorts of interesting things that are rather unusual from the point of view of birds.
Lalitha Krishnan: Did you say to warmer and cooler conditions?
Rohit Chakravarty: Yes, I say that because particularly the studies on bats migrating on mountains have shown that the females go lower down because they mate just before migrating. So, they have a growing embryo in them; the females carry a growing pup and they have to remain active for some period of time in order to let the pup grow in their body. But the males do not have any such pressures so what they do is they actually migrate uphill to much colder conditions where it is easier to go into hibernation. It’s just like us sleeping in winters. We tend to sleep longer in winter because it’s much nicer to sleep in colder conditions. It’s much easier for us to fall asleep in colder conditions so that’s what the males do.
Lalitha Krishnan: Ok and save energy, I guess.
Rohit Chakravarty: Yes.
[Photos courtesy: Pritha Dey. Top:Tanaorhinus kina. Below L-R: Amblychia sp., Naga Hawk moth (Acosmeryx naga), Peach blossom moth (Thyatira batis)}
Lalitha Krishnan: OK. Pritha, back to you. There are day-flying moths and night-flying moths. I know this is a very basic question for you but for all of us who don’t know anything about moths, could you tell us 4 easy ways to help us differentiate a moth from a butterfly?
Pritha Dey: I’m very happy to answer very basic questions. So, moths and butterflies, they both belong to this order, Lepidoptera. Moths came earlier than butterflies. Butterflies evolved from moths. So, there are some connecting groups in the evolutionary tree which are the day-flying moths. So they have bright coloured wings like a butterfly do but mostly moths are nocturnal in behaviour.
The easiest way to differentiate between a butterfly and a moth is to look at the antennas. The antenna for butterflies is club-shaped. They have a round ball-like structure at the end of it whereas moths, they have fuzzy, hairy antennas. Looking at them also, butterflies are more slender but moths are fuzzy and hairy. If you look at them sitting also, butterflies close their wings when they sit on a leaf or a flower and moths sit with their wings open and flat on the surface.
Lalitha Krishnan: OK.
Pritha Dey: Of course, there are exceptions to these things that I’m telling you which actually prove the rule. Another difference is the pupal stage which is very scientific or taxonomic but I’ll still mention it. The moths in a pupal stage spin a covering around their developing stage which is called a cocoon. Which is spun by the moths. But for butterflies, the covering in which the developing stage is there is called chrysalis. It is part of their body that develops into this cover.
Another interesting thing that differentiates moths and butterflies is something called a wing coupling device. In moths, there is a tiny structure called the frenulum which actually joins the forewing and the hindwing but there is no structure like that in butterflies. So, that’s why you find their flight also a bit different. Butterflies, if you see them in flight it’s clearer and in moths, it’s a bit fuzzier and confused flight.
Lalitha Krishnan: OK. And can one see this? Is this visible…the joint between the wings?
Pritha Dey: No. it’s visible under a microscope. So, the last two differentiations that I said are very scientific and taxonomic but for a layperson to differentiate between a moth and a butterfly, is to look at the antenna. That’s the giveaway.
Lalitha Krishnan: This is an easy and practical way for people who might be interested but don’t know how to start looking in their own garden to differentiate the moths and butterflies. Thank you so much. Rohit, since 2016 you have been working on bats in Uttarakhand. Could you tell us more about the bats in the Himalayas?
Rohit Chakravarty: So, Himalayan bats are quite unique. Like Pritha spoke about moths we see very similar patterns with bats as well. Just because of the geographical location of Uttarakhand, there are species that are at the edge of their distribution from Europe, from Eastern Asia like China, Japan, etc. and peninsular India. All of these species sort of merge in Uttarakhand. So it results in a unique diversity of tropical and temperate species. But what is even more fascinating for me is to see these small animals that fly. And flight, as you know, takes up a lot of energy. These small animals live in such elevation and they fly continuously throughout the night. So it’s very interesting from the point of view of physiology to know how these animals do that. At some point in time, it would be great to study these things. There are bats going even further, even in Ladakh which is at 3800-4000 metres. I don’t think there is any place in the whole world where bats occur at such high elevation. That’s unique.
Lalitha Krishnan: One had a concept in one’s head that bats usually live in caves. But now they’re all over urban areas, right?
Rohit Chakravarty: Bats have actually been in urban areas for a very long time. It’s really their ability to keep themselves concealed. Most people have bats in their houses but they don’t know about them until they see a pup lying on the ground or until they see a dead body in their house. But bats really have the ability to conceal themselves. And, they fly out at night, which again helps them conceal. So, bats have been with people for a very long time and it’s just that their secretive behaviour had helped them keep away from people while being close to them.
Lalitha Krishnan: Pretty smart. Pritha, back to you. Could you tell us about the independent project that followed your PhD work?
Pritha Dey: When I came back from Germany after doing part of my Ph.D., I got funding from the Rufford Foundation (UK) where I got to study the moths from the Kedarnath wildlife sanctuary. It is another protected area in the western Himalaya which has not been explored for moths. We know the Himalayan Monal, we know the Musk deer, we know the Rhododendrons from this particular part of Uttarakhand but nothing about moths. In 2018 I did fieldwork there in the summer for two consecutive years. In 2019 also, I did some fieldwork. It’s been a very different diversity that I found from my earlier work in the Nanda Devi Biosphere Reserve because it’s more oak-dominated, rhododendron dominated moist forest in that part of Uttarakhand. I already reported a new species to the western Himalayas from that project. Most importantly I got to do a lot of outreach activities from that project where I could reach out to people from non-scientific backgrounds to talk about moths; how they’re important to our ecosystems and how is it important to conserve them. During that time also, I got to meet you at the Devalsari meet, which was also part of my outreach activity when I could give a talk about moths. Apart from science, I really like to reach out to people about my research which I think is very important for any kind of research. I take that from my independent project.
Lalitha Krishnan: That’s great. And what is the species you discovered?
Pritha Dey: I didn’t discover. it’s an already existing species. It the Drepanid moth which is a hook tip moth that was previously known to be found only in the eastern Himalaya. So, I reported this along with Mr Sanjay Sondhi. He also found it near Chakrata, in a place called Kanasar and I found it in Kedarnath wildlife sanctuary. Both of these records are first-time records from the western Himalayas. That was really something exciting.
Lalitha Krishnan: So cool. This might be a really stupid question but I haven’t heard of a …you know we have a national bird, a national animal, but do we have a national moth? Is that something we could do to promote moths?
Pritha Dey: We don’t as yet but we have state butterflies. We don’t have state moths as of yet. That gives me another reason to talk about moths more and to continue my research.
Lalitha Krishnan: It’s an idea.
Pritha Dey: It’s an idea.
Lalitha Krishnan: Rohit, bats use many senses as you said but mostly their sense of hearing to communicate? You have trapped and recorded their ultrasonic calls. Could you tell us more about how they hunt, how they pick up sounds or avoid threats and stuff like that?
Rohit Chakravarty: Bats use ultrasound to navigate. They make these sounds that we can’t hear. We can’t hear ultrasounds. These sounds that bats make are really loud and sometimes they can be as loud as a firecracker. We are fortunate that we can’t hear it. When those sounds hit objects and come back to them, bats make all these mental calculations in split seconds in their minds where they calculate their distance with respect to the object, their position, their speed, etc. and they navigate. If it’s a hard object, for example, if it’s wood, or it’s a tree or a brick wall in front of them…hard objects reflect almost all of the sound that has hit on them. Whereas if it is a person, or if it’s an animal, that’s in front of a bat, the skin absorbs some sound and reflects part of the sound back to the bat. Depending on the time that it takes for the sound to be emitted and to be returned, and the intensity of the sound that is emitted and the intensity of the sound that comes back to the bats, bats make these calculations and they figure out if it’s an object that’s in front of them – whether it’s an enemy, whether they’re edging toward danger or towards food. So despite our politicians telling us that mathematics is not important, it’s really important for an animal to survive in the wild and they do it subconsciously.
Lalitha Krishnan: I won’t say anything about politicians but bats sound pretty smart. That’s so cool. You also mentioned earlier that bats also feed on moths. I just read part of an article in a scientific journal which mention that a species of tiger moth has developed a defensive ultrasonic clicking technique that jams the sonar–exactly what you were talking about— of echolocating bats to avoid being eaten. They’re saying this is the “first conclusive evidence of sonar jamming in nature”. Who wants to talk about this?
Rohit Chakravarty: I’ll let Pritha answer.
Pritha Dey: Yes.
Lalitha Krishnan: What do they mean by moth-clicks?
Pritha Dey: Moths are majorly predated upon by bats. In the conversation so far we know that bats echolocate to hunt also. They hunt for moths by echolocating. One group of moths known as the tiger moth; they have—you talk about one species—but the entire family has developed this way of combating this echolocation by producing ultrasonic clicks. What they do is basically they produce the clicks at a certain frequency which are also ultrasonic. A frequency that hampers the echolocation of the flying bat and it confuses the bat as to where the moth is located. So, the bat gets confused about the location of the flying moth and cannot really predate on it. So, that’s how it functions and that’s how it evolved. So, the moths echolocate; they produce these ultrasonic clicks only in response to echolocating bats otherwise they do not use any ultrasound to communicate. They are mostly herbivores insects so they communicate only for mating which is mostly through pheromones.
This moth-bat ultrasound warfare is an evolutionary arms race and they are co-evolving new strategies. There is something called a ‘stealth echolocation’ by the bats also where they have devised a way to avoid this sonar jabbing by the tiger moths and at the same time, the moths are also devising new strategies to combat these echolocating bats. So yes, it’s eco-evolving, ongoing warfare in nature.
Lalitha Krishnan: This sounds like something straight out of the movies. You know this could be a hit and miss for both right?
Pritha Dey: Yes.
Rohit Chakravarty: It sounds more like the US and North Korea saying, “My button is bigger than yours.”
Lalitha Krishnan: Haha. Ok. You’ll have both studied abroad. Did anything stand out from those experiences? What did you bring back to your respective fields?
Pritha Dey: For me, I was in Germany for part of my PhD. After I completed my fieldwork in India, I came to Germany to complete the rest of it. My supervisor here (Germany) is a very funny and kind-hearted man who took me to South America and different parts of Europe for fieldwork.
Lalitha Krishnan: Oh nice.
Pritha Dey: I was exposed to a lot of—for the first time—I have seen so many people working on moths come together which I hardly see in India. The efficient networking that they share like all the scientists here – I am talking about the European community – the scientific networking and the taxonomic exchange that is required for lesser-known taxa is very efficient here. Which I took- something positive about my stay in Germany and want to take this culture back to India where more scientists work together toward conserving particular taxa. It would be more encouraging. We have so much diversity in India but very few people working on this kind of diversity. So yes, I took that back from my stay in Germany.
Lalitha Krishnan: That sounds so good. That sounds like a good thing to bring back. What about you Rohit.
Rohit Chakravarty: In the case of Bats, Germany is a great place to study because Germany treats its bats like we treat our large animals. So, bats receive the highest levels of protection in German law. Whereas in India, they are completed unprotected except for a few species. What is even more heartening to see is almost every month, there are citizen science events where people go around the city either recording bat calls in a scientific framework. Or they are citizen groups that put identification rings on bats much like how people put rings to study migratory birds. So groups put rings on bats before they go into hibernation or during autumn. They do this to see how populations are faring in the city or see how populations are migrating from one part of Europe to another. Most of these studies have been going on for decades now. So, this culture of studying bats is really ingrained in them. That’s something I would really like to see in India- to bring it to India and continue for many years to come.
Other than that, of course, Germany is a technological hub. The technology we have here to study bats e.g. miniature GPS tracking devices that you can put on bats to study their movements, study their foraging, and everything. So, that technology is something that I would ideally like to bring back to India.
Lalitha Krishnan: So nice to hear that you’re interested. We don’t have enough of citizen science projects. They’re a good way of creating awareness and conserving wildlife. I’m going to get back to citizen science as both of you are interested. If somebody in India is interested in moths and starts off by taking photographs or wants to id or post pictures online what or where should he/she be looking? What sites or what forums?
Pritha Dey: Yes, you correctly pointed out that both of us are interested in the citizen science framework. There are many forums like the India Biodiversity Portal or different social media groups where people put up pictures of moths and get them identified. Here, I would like to emphasise a particular portal – the Moths of India website which comes under the Biodiversity Atlas Project in India. It is completely citizen science-based. I’m a team member of this initiative. How it functions is that you see a moth, you click a good resolution picture as others can identify it and you can just put it up as an observation with a date and the location. These two things are important. Anybody can register themselves and upload their observations. Then, there’s a team of reviewers. We get these observation uploads every day and we -a team of 7-8 people-we review it, try to properly identify it if it hasn’t already been done and then it is put up on our website. The website is very easily searchable. You can search by location or if you are a bit more oriented toward the moth taxonomy you can search by family or genus names and you can get your moth identified and see their distribution also which is based on whatever observations we have from different parts of the country.
Lalitha Krishnan: That will help. And for bats Rohit? What resources would a bat fan use? What website?
Rohit Chakravarty: So, I have written a detailed article on this and I would really urge the audience to google ‘A Beginner’s Guide to Bat watching’ and the article is up on ‘Conservation India’ You’ll be able to find it as soon as you google it. In that article, I have listed down all the resources that people can refer to, and all the equipment a bat watcher needs to start watching bats and to start identifying bats. Unfortunately, there are not any online portals that allow Indians to know more about Indian bats but there’s a lot of self-learning that people can do and I’m sure this article will help you get started.
Lalitha Krishnan: One could always start a group of sorts, right?
Rohit Chakravarty: Yes and we definitely do need something bat focused in due course of time but at the moment like ‘Moths of India’, we also have ‘Mammals of India’. Of course, we receive a lot more photographs of other large mammals but I would urge the audience to click photos of bats wherever they can find them and post them to groups of ‘Mammals of India’ and also India Biodiversity Portal.
Lalitha Krishnan: OK. That helps, Thanks. I request both of you to share a conservation-related word/concept and tell us why it’s significant for you.
Pritha Dey: What concerns me at the moment is the ongoing insect species decline that we see globally. It has gathered attention from scientists and politicians alike. We need more young people to be interested to study lesser-known taxa or less charismatic taxa from a country which is so hugely biodiverse like India. With the right techniques and tools, India has the potential to stand out in insect conservation. I would really reach out to the young people through this conversation that: Please be interested more in moths, butterflies, and other insects. Apart from science, it’s very important to reach out to the non-scientific community to achieve larger conservation goals and I would end by saying there’s a famous scientific article by the scientist, EO Wilson which says:” Little things that run the world”; he talks about insects and arthropods. As long as you believe that so that’s the message that I would like to spread through this conversation.
Lalitha Krishnan: Bravo.
Rohit Chakravarty: My message is pretty similar to Pritha’s. As someone who works on a lesser-known group of animals. I believe that every animal is different and every animal tells a different story about the world. For e.g. a tiger might tell you a lot about forests and about how deer populations need to be controlled, how human interference needs to be managed, how corridors need to be connected etc. But a bat is a completely different animal and so is a moth and so is a frog. So, every animal tells a different story about the world. And, only when you study them, do you understand what story it conveys and how you should protect its world in order to save the animal itself.
The other message that I would like to younger people is to have faith in science. To not lose hope in science and to develop an objective view of the world; not a subjective one. And to include science in the way we conserve species. Science is not the end result and it’s not the destination but it’s definitely something important we need to incorporate into conservation measures.
Lalitha Krishnan: That was interesting and relevant for anyone who’s listening. Really great. Thank you so much Pritha and Rohit.
I hope you enjoyed this episode of Heart of Conservation Podcast. I’d love your feedback. Do write to me at firstname.lastname@example.org. If you know somebody whose story should be told or is doing interesting work, do contact me.
If you want to know more about Pritha’s and Rohit’s work scroll down for the links. You can download Heart of Conservation podcast episodes for free on Soundcloud, Apple podcast, Spotify, Google Podcast or wherever you listen to your podcasts. Bye for now.
Also, check out “A beginners guide to bat watching
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